Ribozymes are structural RNA molecules which mediate a number of RNA self-cleavage reactions. Two distinct trans-acting ribozymes, "hammerhead" and "hairpin," having different secondary structures have been identified. Oncogenes and Aids (1990) [citation] states:
"Another possible synthetic approach is the development of a chimeric molecule containing a ribonucleotide catalytic center and deoxyribonucleotide flanking sequences. It is also conceivable that chimeric catalysts comprised of an RNA catalytic center and DNA flanking sequences will retain biological activity while having greater stability."
Perreault, et al., Nature, 344:565-567 (1990), describes certain mixed deoxyribo and ribooligonucleotides with catalytic activity. No RNA-DNA catalytic molecules of practical therapeutic utility are known.